The purpose of the proposed experiment is to evaluate the use of transcranial Doppler sonography (TCD) as a screening procedure to detect occupational exposures to commonly used industrial and commercial chemical compounds. TCD has been well established as a noninvasive and cost effective means of measuring cerebral blood flow (CBF) in man. Although the use of TCD in animals has been limited, our pilot work indicates that CBF can be measured in normal greyhound dogs using TCD. Further, we have shown that manipulations of CBF (using CO2) can be detected by TCD. Since changes in CBF often occur prior to behavioral or other clinical manifestations of chemically-induced toxicosis, a means of measuring these changes could potentially be used as an early detection method for detecting exposure to hazardous substances in the workplace. Deltamethrin, a commonly used and very potent agricultural insecticide, has been previously shown to decrease CBF in rate as determined by other techniques. Using a dog model, we propose to expose 10 dogs to deltamethrin at levels comparable to what humans may be exposed to in the workplace. The CBF waveforms of the deltamethrin exposed group will be compared to those of a control group to determine if TCD can reliably detect alterations in CBF resulting from low level exposure to a toxic substance. If changes in CBF can be detected by TCD prior to the occurrence of behavioral or other clinical signs, than interdictive measures could be initiated very early in exposure at a time when the effects of the toxicosis are either minimal or reversible. It is hoped that TCD may soon become a routinely used screening procedure for detecting the early effects of known (and perhaps even unknown) substances on people subjected to potentially hazardous materials is the workplace.